1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device and a method for aging the OLED display device, and more particularly, to an OLED display device and a method for aging the same in which a driving transistor is electrically aged so that the efficiency of the driving transistor is increased to compensate for a lowering of efficiency due to the aging of an organic light emitting diode.
2. Description of the Related Art
A flat panel display device (FPD) has been employed as a display device to replace a cathode-ray tube (CRT) display device because the FPD is lightweight and thin. Typical examples of the FPD are a liquid crystal display device (LCD) and an organic light emitting diode (OLED) display device. In comparison with the LCD, the OLED display device is excellent in luminance and viewing angle and can be made ultrathin because the OLED display device does not need backlight.
The OLED display device is constructed with an organic layer having an organic emission layer, which is interposed between an anode and a cathode. Thus, when a voltage is applied between the anode and the cathode, electrons and holes recombine in the organic emission layer to produce excitons. As a result, light is generated due to the energy of the excitons.
The OLED display device may be classified into a passive matrix type and an active matrix type depending on the method for driving the OLED display. An active matrix type OLED display device is constructed with a circuit using a thin film transistor (TFT). A passive matrix type OLED display device can be fabricated by a simple process since anodes and cathodes are arranged in a matrix shape in a display region. The passive matrix type OLED display device, however, is only applicable to low-resolution small-sized display devices owing to the resolution limit, high driving voltage, and short lifetimes of materials.
In comparison, in the active matrix type OLED display device, a TFT is disposed in each pixel of a display region. Thus, a constant amount of current can be supplied to each pixel so that the active matrix type OLED display device can emit light with stable luminance. Also, since the active matrix type OLED display device consumes low power, the active matrix type OLED display device can be applied to high-resolution large-sized display devices.
An organic light emitting diode may deteriorate due to the usage of the OLED display device. Thus, a driving voltage varies and a lifetime of the OLED display device is shortened. In an initial period of operation, the lifetime of the OLED display device is shortened at a higher rate so that the driving voltage of the OLED display device greatly varies. After a certain period of operation, the lifetime of the OLED display device is shortened at a lower rate, and the OLED display device can be stably driven. Therefore, the contemporary organic light emitting diode (OLED) is intentionally degraded to a certain level using an aging process in order to decrease the initial failure rate of the OLED display device and increase the lifetime of the OLED display device.
The process for aging the OLED, however, may lead to a lowering of efficiency so that the luminance of the OLED display device deteriorates. Therefore, the driving voltage of the OLED display device needs to be increased in order to compensate for the poor luminance of the OLED display device. In this case, the entire power consumption increases.